The present invention relates to noise reducing housing means for a blower motor, which is particularly useful for a vacuum cleaner.
A blower motor includes a motor, typically electric, and a fan driven by the motor for moving air, gas, or the like. Blower motors are often used in vacuum cleaners for sucking air and collected materials into a tank or receptacle. The fan drive motor of the blower motor should be cooled. In bypass type blower motors, a separate smaller fan connected with the fan drive motor blows cooling air over the motor. The flow of motor cooling air is kept separate from the air flow developed by the main blower fan.
It is desirable in a bypass type blower motor, that the air flow through the main blower fan, and particularly from the exhaust of the main blower fan, be kept separated from the motor cooling air flow. Accordingly, housings for supporting the bypass type electric motors and for separating the air flows thereof have been developed, as shown in U.S. Pat. Nos. 3,780,397 and 3,815,172. See also U.S. Pat. Nos. 3,870,486 and 3,063,082.
It is desirable to reduce the noise generated by a blower motor, such as one used in an electric vacuum cleaner. Noise reduction requirements have been mandated for industry and are desirable in domestic applications, particularly with respect to electric vacuum cleaners. Typical blower motor housings, like those used in vacuum cleaners, do not adequately suppress noise. Various noise suppression means are known, but they often reduce the rate of air flow. For obtaining a higher rate air flow, a larger, stronger blower motor is needed, resulting in increased energy costs, or the present blower motor is strained, leading to greater heating or even overheating thereof. Adequate means for suppressing the noise of a blower motor, particularly for an electric vacuum cleaner, without reducing the efficiency of the motor are therefore desirable.
One technique for reducing the noise generated by a blower motor is to reduce the velocity of the air exiting from the housing of the blower motor. This velocity reduction may be obtained by use of expansion chambers or by appropriate baffles in the path of the air. Making the pathway of the exiting air a tortuous or winding pathway also helps reduce the speed of the air and tends to suppress the noise carried along by the air flow. Note the spiral outlets from the blower motor fans shown in U.S. Pat. Nos. 2,982,986 and 2,983,432.
Another technique for reducing noise generated by a blower motor is to move the air over appropriate sound deadening material. The contact of the air with the sound deadening material will tend to reduce the vibration of the air and suppress the motor noise carried along by and conducted by the moving air. Sound absorbing cuffs, or the like, in the flow path of air are known from U.S. Pat. Nos. Re. 21,519; 2,330,701; 3,831,233; and 4,015,683.
However, an effective complete noise suppressing housing means for a blower motor, particularly for use on electric vacuum cleaners has not previously been developed.